An antenna of an electronic device is provided. The antenna includes a substrate including a ground portion, an external metallic frame of the electronic device, a float ground portion arranged to be connected to the external metallic frame in a state of being disconnected from the substrate, and at least one radiator electrically connected to the float ground portion. Upon being fed with power, the at least one radiator may operate as an antenna radiator, or a section of the external metallic frame may operate as the antenna radiator.